Relay construction



April 24, 1951 F, R, MGBERTY RELAY CONSTRUCTION 2 Sheets-Sheet l Original Filed July 29, 1940 F. R. MCBERTY RELAY CONSTRUCTION April 24, 1951 2 Sheets-Sheet 2 Original Filed July 29, 1940 Patented Apr. 24, n1951 UNITED STATES PATENT OFFICE RELAY CONSTRUCTIONr Frank R. McBerty, Mansfield, Ohio, assignorvto The, North Electric Manufacturing Company, Galion, Ohio, a corporation ot: Ohiov Original applicationY July 2,9, 1940, Serial` Nm Divided and this application March c, 1946, serial No. 652,335

9 claims. (cl. 290g-104) Myv invention relates, generally, to relay con-.

structions and. it has particular relation tov the constructionof relays, for automatic telephone exchange systems.

This applicationA is a division of my application Serial Number 348,222, led July 29., 1940. which issued as Patent 2,396,332 on March. 12, 1946.

Among the objects of my invention are: tol

For a more complete understanding ofA the nature and scope of myfinvention, reference may be hadito the following detailed description takenv in. connection withv the` accompanying drawings, in which:

Figure 1 is a, View, in side elevation, certain parts having been broken away to more clearly show the details of;construction, illustratingV one embodiment oi my improved relay constructionr assembled as a` partei?l aline nder or connector link of an automatic telephone exchange o, the relay type;

Figure 2 isy an shown in Figure 1, certain parts beingl shownin section;

Figure 2A is asectional View, Similar to Fig-ure 2, showing in more detail the arrangement of the magnetic circuit;

Figure 3 is a plan View; at an enlargedl scale, showing the arrangement of: one set of movable and stationary contact members;

Figure 4 is a longitudinal sectional View, takenl along the line 4.--4 offFigure 3,;

Figure 5 is a detail sectional view takenl along; the line 5-5' of Figure 4;

Figures 6 through 1()Y illustrate different steps in the manufacture of a contact finger for my*u improved relay construction;

Figure 11 is a plan Viewof a. bank of movable contact members, two, sets being shown, each set being arranged to be individual to` a relay;

Figure l2 is a detailA sectional.l View,Y at an en larged scale, taken along the. lineA [2l- |12 ofV Fig.- ure 1,1; and

Figure 13, is a top plan view showing how the armature is spaced slightly from the glass. rod

stop., member by the metallic reed Which carries? thesame.

endy view of,Y the construction Referring, `now particularlyr to Figures, 11 and= 2 of the drawings, it Will be observedv that thefref-f. erence. characters |02 and II each designate. generally, a relay construction. Each or these relay,` constructions may comprise whatisknown in the telephone arti as atens relay, ten of which are mounted in, alignment to provide the` tens relay of; aline iinder or connector link, as is disclosed in4 more detail in myv copending ape` plication Serial No. 348;.22-3, led July 29, 19.40,- novi,r Batent, No. 415337, issued` February 11',

1947. Since the construction of the relays I0'v and II is.V identical, only one of them will be defA scribed' in detail' 118176111.

As shQWn.- irl .Figures 2- and- 2A of they draw;

insa, each; relay is provided with a magrlctic circuit.: whichv may; be that, of an electrcmaenet hadllg a brQali pple piecel with a suitable magg netic return, The` toward pole piece may take. the form c f a :'l' and tiicrcturnpole piece mayv have the form ci an interttine U member corri-V prising side plates I2 andthe back-bar I3.

TheliWO`Sidedmagnetic structure is designed to receiyeon each oft its,V sides, groups ofarma? tures whereby theigloups of armatures are atedf uponk by.` ,sub'stantially.` equal portions of the, flux. generated in theM core and.` thereby respond in,

substantiallyv equal acts; to equal forces.

As will hereinafter appear, instead of employ,.Y ing.- two side plates I2 andvv a. back bar I3,l the side plates I/2 may be` integral with each othery and provide a generallyA li-shaped conguration.

which can be mounted on a separateY back bar. or other support,V as may be desired. Since the members making up the magnetic circuits as herein disclosed are formedof` silicon steel., this, alternate constructionr is preferable, i11- some cases, since it is. then, unnecessary to construct. theback bar i3, of silicon steel. Instead, it may be constructed of other` cheaper material.

The 'FY-shapedmagnetic memberV which inten-L tsl with thev u-shaped magnetic member com; prisesy a pole. piece I4 and a core. I5.

I5 comprises the stem of U16 T and around it' isA positioned. a winding` or coil. I6. of conventional.

I5 may be secured to the back design. The core piece III by. pressv fits, if it bar I3 and the pole is. not desi-red tov provide for ready removal of:

the coil IB.. Ii it is desired to permit ready rei moralof the coil I6, then thepole piece I4 should,

be arranged to be readily detached from the core.

I or they core I5. should be arranged to be readily detached fromv the back bar I3.

'1j-he 991e piece. I4u isy of such material dimensions with relation te ille .Uvshipd me?? The core.

3 ber, the core I5 and the coil l5 that the flux generated by the coil is as nearly as possible equally distributed between the two sides of the pole piece and throughout the length of each side.

It will be observed that air gaps I'I are provided between the ends of the U-shaped magnetic member formed by the side plates I 2 and the back bar I3 and the ends of the top of the T-shaped magnetic member formed by the pole piece E4 and the core I5. These air gaps are preferably about ses inch long. However, these air gaps bear a certain necessary relation to the size and material of the armatures and their proximity to the pole piece, as will be fully described later.

With a view to accurately Valigning the side plates I2 of the U-shaped magnetic member with the pole piece I 4, clamp plates 20 are provided on opposite sides of the side plates I2 and are secured in position by means of screws 2l which are threaded into the ends of strut members, one of which is shown at 22. It will be observed that the strut members 22 serve not only to provide a clamping action between the upper ends of the clamp plates 20, but also that they serve to space them and the side plates i2 apart.

Positioned on top of the pole piece i4 and common to both of the relays l0 and I l is an insulating block 23 which is secured in position by' screws, one of which is shown at 24, which project through the pole pieces I4 and into the upper threaded end of a strut member 25` the lower end of which is threaded into the back bar I3. The insulating block 23 is preferably formed of mouldable material, such as a thermoplastic. Along the edges of the insulating block 23 are moulded anvil contact members 2B which form the stationary contact members of the relays. The term anvil is employed herein to characterize a contact member that is rigidly and E rmly mounted and against which another contact member reacts in the manner that a blacksmith causes his hammer to strike his rigidly and firmly mounted anvil. As is shown more clearly in Figure 4 of the drawings, each of the anvil contact members 26 is provided with a reentrant portion 2'I about which the material forming the insulating block 23 is moulded to securely grip the anvil contact members in position.

Referring again to Figures 1 and 2 of the drawings, it will be observed that the anvil contact members 2E are provided with extensions 26a, 2Gb, 26o, 26d, etc. The extensions 26a, 2Gb, 20d, etc. are arranged in staggered relation of decreasing lengths and their upper ends are turned outwardly as indicated at 28 and notched as indicated at 29. This staggered arrangement of the extensions is provided in order to facilitate connection thereto of paralleling conductors which can then be positioned in coplanar relation. As is described in detail in my copending application, referred to hereinbefore, corresponding extensions 26a of the relays l0 and il are connected in parallel circuit relation by a wire which is secured in the notched portions 29 by being spot welded therein.

It will be observed that the upper ends 28 of the extensions 26o are turned inwardly rather than outwardly as is the case respecting the other extensions. Thisconstruction is employed since these extensions are not paralleled with any other extension of any other relay in the link. In order to permit the conductors connected to extensions, such as the extensions 26o, with conductors arranged in coplanar relationship, these extensions on the several relays are staggered by having the upper end portions 28 of diierent heights.

It will also be observed that the extensions 26a, 20h, etc., on one side of the insulating block 23 are offset with respect to the corresponding extensions on the other side. The purpose of this offset relationship will be presently apparent.

The anvil contact members 26 and their extensions are formed of good conducting nontarnishing material such as German silver. In the embodiment of the invention shown in the drawings they are 0.080 inch wide and sie inch thick. The lengths of course vary depending upon the length of the extension individual thereto.

Individual to each of the anvil contact members 25, there is provided a contact linger which is designated generally at 32. Each contact linger 32 comprises a metallicreed 33 in the form of round wire which has good electrical conducting quality and is highly resilient and corrosion resisting. 'I have found that stainless steel Wire, known as 18-8, and having a diameter of 0.016 inch, is highly satisfactory for my purposes.

Mounted on the upper end 34 of each of the metallic reeds 33 is an armature 35 which serves not only to ex the metallic reed 33 on energization of the winding I5 but also it serves to conduct current between the reed 33 and the associated anvil contact member 25. It is noted that the armatures 35 bridge the associated air gaps I'I. The armatures 35 are so mounted with respect to the adjacent edges of the pole pieces I 4 that an air gap of 0.032 inch is provided therebetween. It is possible to increase this air gap to 0.053 inch but the smaller air gap is preferable. When the armature 35 has been moved into its alternate position on energization of the coil I6, there is provided a residual air gap between the armature 35 and the adjacent edge of the pole piece i4 of from 0.010 to 0.012 inch. It will then be apparent that the movement of the armature 35 from one position to another is about 0.020 inch.

The armatures 35 are formed of material which not only has good electrical conducting properties but also material which is magnetic. I have found that material known as Alleghany metal No. 4750 is entirely satisfactory for this purpose. Each of the armatures 35 is preferably about 0.478 inch long, about 0.080 inch wide and about 0.0429 inch thick.

The lower ends 33a of the metallic reeds 33 project beyond insulating support members 31. The insulating support members 3l are formed of the same material as the insulating block 23 and,` as will hereinafter appear, the metallic reeds 33 are especially prepared so as to make certain that they will be securely held in the insulating support members 3I on completion of the moulding operation.

Referring to Figure l of the drawings, it will be observed that the projecting lower ends 33a, 33h, etc., of the metallic reeds 33 extend dow wardly through the same distances. It will also be observed that the lower ends 33d, 33h, etc.', on one side of the relay construction are offset with respect to the corresponding lower ends 33a, 33h, etc., on the other side. This arrangement is provided in order to permit the coplanar arrangement of cross connecting conductors between corresponding tens relays of adjacent links as is described more fully in my copending application, referred to hereinbefore. The cross connecting conductors .are secured by suitable means; such; asf'. weldingtftog-the; lowermost nur Sincefthe anvil contact members-'26 are arranged irr` alignment with their:V respective contact fingersfZS,Y thereason for: the olset positions of the anvil-.contact membersZi-onrthe opposite' sidesy ofi the insulating block 23: will nowf be apparent:

The insulating support; members; 31- in which aresmoulded the metallicA reedsr33-maybe secured inipositionon: the backzbar- I 3 fby; meansrof screws 38: These screwsf alsoserve to: carry support membersl 39which are arranged. tor support con'- ductor brackets carrying conductors-L extending underneathA the relays landl I. Asis-set forth intdetailiA in"V my copendingA application, referred tovhereinbefore, certainoi? the downwardly extendingends 33a; 3373,; etc'., oi themetallic reeds 33', are. arranged to` be connectedin parallel in their respective-links; while the remaining down.- wardly projecting end portions are. arranged to be cross connected as described.

Asshown-more'clearly in Figures. 3; 4 and 5 of the"L drawings, each of the armaturesj-35l is` provided with anxerosion resisting contact member 4l in theform of a' short lengthoff roundwire; 'Ihac'ontact'Y member M is preferably formed of good. conducting material .whichn will resist ero;-

sion: duev to abrasion andA arcing. I havefound' that round wire formed of palladium is satisfactory for this purpose. A. wire having azdiamet'er of.0.f020 inch and a length of about 0.070 inch of thiszmaterial is welded; as shown, across oneface of' the*A armature 35" to provide the contact engaging surface thereof.

Each1ofthe anvil Contact members 26 is liliewise provided with erosion resisting material. As shown, thiscomprises an insert 42 in the lower end; of each of the anvil contact members 26. Thel inserts 42 may be formed of palladium and arey inlaid by conventional means in a strip of German silver from which the anvil contact members-and their integral extensions are cut. The insert 42v is preferably about 12- inch wide and about 0.010 inch thick. As indicated at 43, each ofthe` inserts 4'2 is grooved intermediate itsends so as., to provide two distinct points of contact engagement with the. generally cylindrical. contact mem-berA 4| carriedv by the armature 35; in the event that the alignment between the armarr tureL 35V andthe anvil. contact' member 26. isl not such as: to initially cause both. contact engager ments. to take place, it will be obvious: that. the armature 35 Will beturned slightly duel to the pull. of the fluxr` generated by the coil. I6, so; asV to cause the two point contact engagementY as defscribed.

It is highly desirable that thel armatures 3.5v associated with each side of. each of the'relaysl Ill and H be accurately aligned so that uniform air gapsV are provided between them and the ad.- jacent edges of the pole pieces I4. For this purpose,v as shown in Figure 2 of the drawings, the metallic reeds- 33 are so arranged that theytendx to bias the armature 35 outwardly toa position beyond the normal open circuit position.

The stop memberr 44 of suitable, hard, rigid and non-hygroscopic` material such asv Pyrex glass.. is positioned along the armature 3.5 and isl so located that the inherent resilience of theV metallic reeds 33 urgesarmatures: 35.*towa1d. the`V glass-rods 4.4.. Ars-,shown in. Figure 11.34.. the .armee turefeS-iitself; does not-rest against' the-glaSS-rodsi 4'4; but? rather." it: is spaced., slightly therefromn by theu upper; endg portion 34l of;v the*V metallicf reed 337: ha-rdi'metal; stainless isteel; as.. comparedywith` the armatura. 35,y Alleghanyl metal, and further since itmakes.substantially/only point Contact with. the glass `rodzdfi .thereiis ga minimumofjwear andf production.y of I; metal dust-which would otherwise-` be the casel if" the; armature.` 35 itself were; Perf miti-ed.I to strikeV the.. glass rod 44. The importance ofi this-t feature willA be; appreciated more: fully; when ittisyrecalled that the-armatures. 3.5;

are operated. many millionsaof times duringV the. lifeof: thesrelay of" the type here concerned.y

The`1 glass rods 44:; are held,A in positionv by means4 of; suitable non-magnetic clamp members.

45;# which;arer'heldinplace by the screwsLZl.y It; isA the4 common experience in apparatusyof. thew resting position; oxides and impalpablemetallic.

powders.: form.; dustv accumulates; the moisture when. present consolidates these extraneous: ma.;-

te-rialszinto.adherentzscales or adhesive cements thedeleterious action. of which is increased.- as. the contacting surfaces are hammered; down. intoclose tting surfaces; Theser eiects. disturbing to'. thev operation, vary. with temperature, moisture andfrequency of operation and require a: large; factor of. safetyA in the for-.ces requiredy to'` move the movable part from its resting anvil. In` the course ofi a. relatively short period, such parts require cleaning and;.inv themeantime, increasingly frequent. and.: irregular failures of operationV may take place. The moving parts--i armatures and/reeds-in the inventionV here.- de.-

scribed, bea-r'upon their resting anvils with slight.

force, merely enough to iix accurately the posi--A tion of." rest, and are intended to be operated upon by. minimum attractive forces, since by thesemeansthe energy consumed by the device and the detrimental and destructive effects of the motion are reduced to a minimum and the speed. of operation is increased.

The stop-rod 44 of Pyrex or equivalent glass, is straight.. inflexible, unchanging under normal temperatures; itv is. not deformed by. the impact.` of .the partsresting upon it; it suffers no chemical change, accumulates no moisture or dust, it changes; temperature slowly and; does not freeze the armatures ;fand in no way injuriouslyV affects the. metal. parts restingupon it; In fact the operation, of: the armatures hundreds of millions of times, equivalent to the thousands of yea-rs of; commercial ope-ration, exhibits practically n0.: alterationl in the characteristics of operation.y It must` bek assumed that the impact of the ree. turning armature upon the glass. rod transmitted. through; the: projecting part of the upper end portion 3 4 of theV reed 33 must expend in heat its energy of motionr and, must create some vibra--V tion; but it is found that the period of. vibration is of. s uh bien frequency and so.r brief: as to.;

Sincetheflreed- 33;.; is formed ofJ relatively.L

hardly detectable in a cathode ray oscillograph.

Not only do the glass rods or stop members 44 align the armatures 35 so that uniform air gaps are provided, but also they serve to prevent oscillation of the armatures 35 on the deenergization of the coil I6. As soon as the armatures 35 engage the stop members or glass rods 44 through the upper end portions 34 of the metallic reeds 33 they are immediately brought to rest without vibration or chattering.

It will be noted that leads 45 from the coil I are brought out and are connected to metallic reeds d?, which also extend through the insulating support members.

In Figures 6 through 12 are illustrated the steps involved in making up a set or bank of contact nngers 32. Of course, the sequence in which these steps are performed may be varied, the sequence that is set forth hereafter being one that has proven to be highly satisfactory.

The metallic reeds 33 of 18-8 stainless steel should be straight in order to permit assembly into the contact bank in such manner that no adjustments are required once the relay assembly has been completed. As shown in Figure 6, each metallic reed 33 is deformed as indicated at 49 intermediate its ends to provide a flatttened portion. The maximum thickness of the flattened portion 49 is preferably about 0.012 inch. The flattened portion 49 is provided in order to prevent turning of the metallic reed 33 after it has been moulded in the insulating support member 3l.

The end 34 is then positioned in a slot 50, Figure '7, in the armature 35. lThe slot 50 is slightly less in depth than the diameter of the metallic reed 33. With a reed of 0.016 inch diameter, the slot 50 has a depth of 0.014 inch, thereby leaving the reed to project above the surface of the armature 0.002 inch to facilitate welding, as will hereinafter appear, and to provide substantially point contact with the glass rod 44.

The armature 35 with the end 34 of the metallic reed 33 inserted in the slot 50 is then placed between the jaws l, Figure 8, of a suitable press which are moved toward each other, as indicated by the arrows in order to deform the walls of the slot 5G about the end 34 of the metallic reed.

Next, as shown in Figure 9, the palladium wire contact member if is welded on to the outer end of the armature on the side away from the end 34 of the metallic reed.

The required number of contact fingers 32, assembled as described, together with the necessary number of coil connectors fi'i, are assembled in a suitable mould and the insulating material is moulded in position about the nattened portions 49, as shown in the nnished product illustrated in Figures 1l and 12.

It will be observed that two sets of contact fingers 32 for two tens relays form a unitary construction through the use of a single insulating support member 3l, to both sets. Obviously, the contact lingers can be assembled in single sets, if desired. It will be noted that one end 52 of the insulating support member 3l is notched outwardly while the other end 53 is notched inwardly. This construction permits overlapping of the adjacent ends of adjacent insulating support members of adjacent tens relays so that a single screw can commonly support both of them.

In a preferred construction, insulating support member 3i' -is 15g" wide. The metallic reeds 33 project above the support a distance of 121/64".

They project below the insulating support 31 onehalf inch. In a typical link assembly certain of the lower projecting portions 33a of the contact fingers 32 will be longer than others in order to provide for longitudinal connection therewith with respect to the link. The other downwardly projecting ends will be of the same length to facilitate cross connections between the links by conductors in coplanar relation as described.

After the contact fingers 32 have been moulded in the insulating support member 3l, the armatures are commonly positioned on one electrode 54, Figure 10, of an electric Welder. A welding wheel 55 is then moved relative to the armatures 35 so as to successively engage the projecting portions of the ends 34 of the metallic reeds 33. On now of current between the wheel 55 and the electrode 54 through the metallic reed and armature the latter two are securely welded together' as will readily be understood. rThe reason for having portions of the metallic reeds project above the armatures 35 in the grooves 58 therein will new be more clearly apparent.

Since certain further changes may be made in the foregoing described constructions and diiferent embodiments of the invention can be made without departing from the scope thereof, it is intended that all matter contained in the above description or shown in the accompanying drawings shall be interpreted as illustrative and not in a limiting sense.

I claim as my invention:

in a multi-circuit controlling relay, the combination of an electromagnet, multi-contact armature means responding simultaneously 'thereto cor` "ising a row of ilexible wire reeds each anchored at one end, armature plates of magnetic material secured to the other ends of said reeds, contact means carried by said armature means for controlling individual circuits, and a common back-stop for said row of flexible wire reeds comprising a rod of insulating material extending transversely across the back side of said row of reeds, each of reeds having a cylindrical rear surface and said back-stop rod havinU a cylindrical front surface, whereby the contact between each reed and said back-stop rod is the point contact of two cylindrical surfaces engaging each ther substantially at right angles.

2. In a multi-circuit controlling relay, the combination of an electromagnet, a row of flexible wire reeds each anchored at one end adjacent to said electromagnet, individual armature plates of magnetic material secured to the other ends of said reeds, all of said armature plates and reeds responding substantially simultaneously to the energization of said electromagnet, individual movable contacts carried by said armature plates, stationary contacts adapted to be engaged by said movable contacts for multi-circuit control, and a common back-stop for all of the flexible wire reeds in said row comprising a glass rod extending transversely across the back side of said row of reed, each of said reed having a cylindrical rear surface and said back-stop rod having a cylindrical front surface, whereby the contact between cach reed and said back-stop rod is the point contact of two cylindrical surfaces engaging each other substantially at right angles.

3. In a multi-circuit controlling relay, the combination of an electromagnet, a row of flexible wire reeds each anchored at one end in proximity to said electromagnet, individual armature plates 1 of magnetic material secured to the free ends of said reeds, all of said armature plates and reeds responding substantially simultaneously to the energization or said electromagnet, individual movable contacts carried by said armature plates, stationary contacts adapted to be engaged by said movable contacts for multi-circuit control, and a common back-stop for all of the iiexible wire reeds in said row comprising a hard-wear resisting type insulating rod extending transversely across the back side or" said row of reeds substantially directly in rear of said armature plates, whereby to absorb the return stroke inertia of said armature plates in. their movement away from said stationary contacts without causing fore and ait iiexure or" their individual supporting reeds, each of said reeds having a cylindrical rear surface and said back-stop rod h a cylindrical front surface, whereby the Contact between each reed and said back-stop rod is the point contact of two cylindrical surfaces or` hardwear resisting materials engaging each other sub stantially at right angles.

4. In a multi-circuit telephone relay of the class described, the combination of an electromagnet, multi-contact armature means responding simultaneously thereto comprising a row or flexible wire supporting reeds each anchored at one end, each of said reeds being of cylindrical cross-section, individual armature plates of magnetic ma terial secured to the iree ends of the reeds, all o said armature plates and reeds responding substantially simultaneously to the energization ci said electromagnet, individual movable contacts carried by said armature means, a row of stationary contacts adapted to be engaged by said movable contacts for multi-circuit control, each of said armature plates having a slot therein extend ing longitudinally of its rear surface', the individual supporting reed associated with each plate being secured in said slot with a portion of its cylindrical surface protruding rearwardly from said slot to form a cylindrical stop surface, and a common back-stop for all of the flexible wire supporting reeds in said row comprising a wear resisting type insulating rod extending transversely across the back side of said row of reeds and arranged to be engaged by those portions of said reeds which protrude rearwardly from the slots in said armature plates.

5. In a telephone relay, in combination, a relatively small diameter iiexible metallic reed xedly mounted at one end, an armature plate of magnetic material relatively wide as compared to the diameter of said reed carried thereby at its other end with a cylindrical portion of the reed extending therefrom along the back side thereof, a movable contact carried by said reed, a stationary contact adapted to be engaged by said movable contact, means for attracting said armature plate to move the armature plate and movable contact toward said stationary contact, and a cylindrical stop of relatively hard wear and corrosion resisting insulating material extending transversely of said armature plate and metallic reed and arranged to be engaged by said portion of said reed projecting from said armature plate to limit movement of said armature plate away from said stationary contact.

6. The invention, as set forth in claim 5, wherein the cylindrical stop is a round glass rod.

'7. The invention, as set forth in claim 5, wherein the metallic reed is o stainless steel and the cylindrical stop is a round glass rod.

8. The invention, as set forth in claim 5,. wherein the armature plate is formed of relatively soft material likely to become disintegrated if allowed to contact the stop, the reed is formed of relativen ly hard stainless steel capable of withstanding repeated impacts with the stop without disintegration, and the stop is a round glass rod,

9. In a telephone relay, in combination, a rela tively small diameter flexible non-corrosive metallic reed fixedly mounted at one end, an armature plate of magnetic material relatively wide as compared to the diameter of said reed carried thereby at its other end, a movable contact carried by said metallic reed, a stationary contact adapted to be engaged by said movable contact, electromagnetic means for attracting said armature plate, and a stop of relatively hard wear resisting glass material extending transversely of said metallic reed and armature plate and arranged to be engaged by said metallic reed to position said armature plate with a minimum of chatter for subsequent reoperation with each deenergization of said electromagnetic means.

FRANK R. MCBERTY.

REFERENCES CITED The following references are of record inthe r i'lle of this patent:

UNITED STATES PATENTS Number Name Date 322,139 Thomson July 14, 1885 1,082,310 Erickson i Dec. 23, 1913 1,318,178 Reed Oct. '7, 1919 1,462,585 Soreng July 24, 1923 1,521,591 Beck Jan. 6, 1925 2,423,524 Side July 8, 1947 FOREIGN PATENTS Number Country Date 468,974 Great Britain July 16, 1937 

